Ok, I have to do some posts in the newbies forum to get greater access, so I'll try to share something worthwhile.

I've been mining for about a week now and my head is spinning from all the reading I've done on the topic. A key factor in profitability of mining is obviously cost of the power to run the equipment, especially for an amateur user like me who just wants to get some value out of a graphics card. I have a power meter, so measuring my current wattage is as easy as plugging the box into it.

The hardware in my box is bottom-end gaming and is about 15 months old. I bought what I think is good quality brands but economical hardware and it's proved faultless so far. In particular I made an effort to get an efficient (but value for money) PSU, so unbranded equipment at least will probably use a few % more power than mine.

The PC often is left on during the day for a number of hrs, let's say 10.5hrs average.Daily cost = 10.5hrs * (42.5W/1000W) + (24hrs - 10.5hrs) * (69.5W/1000W) * $0.21168/kWh = 1.3845kWh * $0.21168kWH = NZ$0.29307096

It's winter in NZ right now, so the waste heat actually saves on space heating too. Our heat pump (fairly old) is probably 2.5:1 efficiency or worse, so the actual net cost is probably more like NZ$0.20/day.

(If I couldn't make good use of the waste heat and the time the PC was on, the cost would be about NZ$0.353)

NZ$1 = approx US$0.80 I think, so net power costs are about US$0.16/day

My earnings over the approx 5 days I've had the GPU mining set up have averaged about 0.15BTC/day through pooled mining, which if valued at US$15 per BTC would earn me US$2.25/day for my 16 cents.

If I'd done some work in the office instead of writing this, I probably could've earned more than a weeks mining, but I guess it's nice to have an interesting hobby...

ps: My GPU output drops by around 10Mhash/s when leaving Firefox open (with about 20-30 tabs open mind you, due to my crazy browsing habits)

I think I will investigate underclocking the memory, then overclocking until it reaches a similar running temp, being 74-76 degrees.

After my initial post, I realised I forgot to include the power cost of my ADSL 4-port modem router, which uses about 10 watts (but is used for part of the day for other things too), but it won't affect the economics of mining substantially.

I run my 6770 at 960mhz. it jumped 20 watts from 800 to 960mhz my hasing went from 185 to 212m/hash sec.

Im running it on 5-6 year old dell. My kill a watt meter says im pulling on average 240watts (240 x 4 =kwh) hashing away which at 7 cents per KWH cost me roughly (6 x .07 = ) 42 cents a day. At current rate of my pool I am averaging $1.78 income a day and expense of 42 cents.

You bring an interesting point, there might be a certain clock speed that maximizes profits. I have not down clocked the memory yet either. Ironically, this old Dell uses more watts then a 3.6ghz quad core AMD with power savings features toggled off and overclocked 6850 to 875mhz by 15-20 watts. Looking forward to my new sempron build :-)